The targets are special version of the normal enemy which simaris will inform you if the target will spawn in that mission.
They'll be marked on the minimap once you're in range and will have 4 glowing spots if you zoom in with your scanner.
Once you scanned all 4 spots, it'll go boom!
edit: I've just noticed that when i zoom in with simaris's scanner, there will be some blue light thingy floating around. These lights are actually a path that lead me directly to the target.
So, yeah, we can just mindlessly follow them lights and not actually hunting anything.